Optical detection of the anomalous X-ray pulsar 1E 1048.1-5937 following a glitch
ATel #1071; Z. Wang, C. G. Bassa, V. M. Kaspi, R. Dib, C. Tam (McGill)
on 10 May 2007; 17:50 UT
Credential Certification: Z. Wang (wangzx@physics.mcgill.ca)
Subjects: Optical, Neutron Star, Pulsar
Referred to by ATel #: 1121
Following the sudden spin-up and increase in the X-ray flux of
the anomalous X-ray pulsar 1E 1048.1-5937 at the end of March
(Dib et al. 2007; ATEL #1041) and the subsequent brightening of
the near-IR counterpart by ~1.5 magnitude in the Ks band
(Wang et al. 2007; ATEL #1044), we report a similar brightening
at optical wavelengths. We were awarded a DDT optical imaging observation
from European Southern Observatory (ESO), and observed the field of
1E 1048.1-5937 on 2007 May 8, UT 00:01, at I band, using the optical
camera FORS2 on the Very Large Telescope. The exposure was 46 min and
the seeing 0.5 arcsec. We detected the optical counterpart identified by
Durant & van Kerkwijk (2005, ApJ, 627, 376), and found I =24.9+/-0.2 mag.
It is interesting to note that like the brightening in Ks band,
the source in I band was 1.3 (+/-0.4) mag brighter than in 2003
June (Durant & van Kerkwijk 2005). This may suggest that the optical and
near-IR emissions from this AXP are related. Further optical
observations are encouraged.
We thank ESO for granting us this DDT observation and Ferdinando Patat
at the Users Support Department of ESO for making the data accessible
to us right after the observation.
